LONDON, April 18 (AFP) - Britain will repatriate thousands of Kosovo refugees who fled there during NATO's bombing campaign last year.

Home Secretary Jack Straw said 3,000 refugees still in Britain would have to leave by the end of June because their 12-month permit to remain will soon expire.

"It is broadly safe for those of Kosovan Albanian extraction (to return) and for that reason we've made it clear that exceptional leave to remain, which runs out between April 25 and the end of June, will not be renewed unless there are very exceptional circumstances," Straw said late yesterday.

"Enforcement action will be taken in due course against those who are unwilling to go back voluntarily," he said. "But we will encourage them to go back voluntarily. A lot of work is going on to achieve that."

The Times reported today that two flights had been booked for May and two more for June to return the refugees. Each refugee will be given STG250 ($A673) to help them resettle, it reported.

The Refugee Council criticised the British decision, saying that some of the refugees were in no fit state to return to the troubled Serbian province.

"The people who came to Britain were chosen on the basis of vulnerability," said the council's director of communications Fazil Kawani. "Of those remaining in the UK, many are not yet ready to return.

"Some may be receiving medical treatment for serious conditions, such as cancer, and some will still be suffering the consequences of the trauma they experienced or witnessed."

The refugee issue comes at an emotive time in the world of British politics, where the Labour government and Conservative opposition are engaged in an unseemly row over who is the tougher when dealing with asylum and immigration.

Conservative leader William Hague is planning to unveil a tough blueprint to pander to the large anti-asylum constituency in Britain, the press reported today. Hague wants to detain all asylum seekers and rush through their applications for asylum, newspapers reported.

Hague's proposals, set to be unveiled later today, will be "provocative", The Daily Telegraph said, but his party believes that "the public is ready to support strict new controls to stop the growing numbers of illegal immigrants."